RAT 5 wrote
"Using FPA only would be like, in a less sophisticated a/c, setting a V/S at FAF and starting the watch and hoping."
As I understand it, the FPA or Flight Path Angle is Inertial based,; it certainly isn't just a V/S you set. As the ground speed varies, the aircraft position relative to the desired FPA is adjusted by the autothrust to maintain the correct FPA. The idea of a Continuous Descent Approach, is that the aircraft is configured in the landing configuration and continuous descent, at Vapp and the FPA places you in a position relative to the runway for a Threshold Crossing Height of 50. With no thrust changes , or changes in rate of descent you should be at the MDA in a position to see the runway, disconnect autopilot and continue to landing..
In the old "Dive and Drive" LOC approaches, you would have a Missed Approach Point defined by a DME value or cross radial. Once you are past the FAF descending to MDA, then increase power to level off, and at the MAP (Missed Approach Point) if runway is not in sight, it's a Go Around.